Smilax (Greenbrier)

Smilax rotundifolia (called the bullbrier or roundleaf greenbrier) is one of three very common greenbriers in SC. Here it is sprawling over Chinese privet along a creek. Leaves are large, shiny, rounded, and solid green.
Joey Williamson, ©2016 HGIC, Clemson Extension

Smilax species (greenbriers) are difficult to control weedy vines that will entangle through ornamental landscape shrubs. These vines are native to North America. In South Carolina, there are ten common Smilax species, along with five less common species. Many common names appear for these troublesome vines, such as catbriers, greenbriers, hogbriers, bullbriers, prickly-ivies, deer thorns, and smilaxes. They are evergreen to partially deciduous plants, produce strong tendrils at joints to aid in support, and are armored with stiff thorns along the vines. Greenbriers are perennial vines and capable of growing under low light conditions, which allows for rapid growth beneath shrubs to become well established.

Greenbrier vines are dioecious, which means there are separate male and female plants. The female plants produce small, ¼- to ½-inch blue-black, black, or red fruit, formed in small clusters. Birds and small mammals often consume these fruit in winter and spread the seed.

The root systems of greenbriers are typically very extensive, knobby rhizomes that are extremely difficult to pull out of the ground. Each rhizome may sprout additional fast-growing vines from several inches to several feet from the original vine.

The rhizomes can quickly regenerate new vines after being cut, damaged by fire, or treated with weed killers.

Larger greenbrier vines are capable of growing upright at least six feet. The production of tendrils allows the vines to stabilize their height by tightly hanging onto shrub branches and low-hanging tree limbs. These tendrils are actually modified stems that start green and pliable but once wrapped around a branch or twig of a nearby woody plant, they mature and harden. Impenetrable thickets of these thorny vines are often encountered, where they have sprawled over and between nearby shrubs and trees. Using woody plants for support, greenbriers may grow as high as 30 feet.

Most species of greenbrier in SC have blue-black or black fruit that contain from one to three hard seeds; a few species have red fruit.
Joey Williamson, ©2016 HGIC, Clemson Extension

The long, sectioned greenbrier rhizomes have nodes where roots and new vines arise.
Joey Williamson, ©2017 HGIC, Clemson Extension

Greenbriers, such as this roundleaf greenbrier, grow tall and attach to woody plants for both support and additional height by tightly holding onto branches with tendrils.
Joey Williamson, ©2016 HGIC, Clemson Extension

Greenbrier thorns (actually prickles) may be green and quite small on some species or very large and multi-colored on mature vines of other species, such as on the saw greenbrier (Smilax bona-nox), another one of the common greenbriers in SC. These thorns actually aid in the support of the vines as they snag on nearby branches of shrubs and trees. Some species also have spines along the margins of the leaves to aid in defense from animal browsers.

Smilax bona-nox (called the saw greenbrier) is one of the three very common greenbriers in SC. Its mature vines are armored with large, stiff thorns, and the stems are scurfy (i.e., with a scaly crust on the stem surface).
Joey Williamson, ©2016 HGIC, Clemson Extension

Smilax bona-nox has uniquely shaped leaves with basal lobes, the foliage is mottled (lightly spotted with pale green), and the leaf margins have small spines. The fruit are black.
Joey Williamson, ©2016 HGIC, Clemson Extension

A third common greenbrier in SC is Smilax glabra (called the cat greenbrier), which can be distinguished from other species by its pale-colored, lower leaf surface. The leaves are typically mottled (that is, lightly spotted) but have no spines along the leaf margins.

Smilax glabra (called the cat greenbrier) has a pale-colored, lower leaf surface (glaucous), bluish-black fruit, and no spines along the leaf margins.
Joey Williamson, ©2016 HGIC, Clemson Extension

Not all greenbrier vines are troublesome weeds. The lanceleaf greenbrier or bamboo vine (Smilax smallii) is practically thornless and makes a very attractive climbing vine for training on trellises. The leaves are shiny green, and the vines will grow to approximately 8 feet high. Its fruit are initially a dull brick red but eventually turns reddish-brown at maturity.

Control

Chemical control of greenbriers is difficult because their extensive root system can regenerate new vines from further back along the knobby rhizomes, and the waxy foliage resists the uptake of sprays. If the greenbriers to be controlled are only a few small individual plants, it is possible to dig up the rhizomes. However, if it is a larger vine, then chemical treatments will be necessary.

Because most chemical sprays may not penetrate the waxy coating on mature foliage, cut the vines and spray after they re-sprout tender new growth. Wait until the regrowth is ½ to 1 foot tall and spray with a 10% solution of glyphosate. To make a 10% solution, add 13 fluid ounces of a 41% concentrate glyphosate product with enough water in a pump-up sprayer to make a gallon of spray. Alternatively, wait until early spring to spray new growth. See Table 1 for examples of products containing glyphosate.

Beneath desirable shrubbery, cut the vines near the soil line and pull out the vines. Immediately paint or spray the freshly cut vine stumps with a 10% glyphosate solution, but do not allow the herbicide to touch landscape plants. Glyphosate has very little soil activity and should not be absorbed by the roots of nearby landscape plants.

Triclopyr is a broadleaf herbicide that is absorbed by the mature foliage of greenbrier vines. Spray the foliage with a solution of triclopyr (9 fluid ounces of a 61.6% product with water to make a gallon of spray, or a 50:50 mix of an 8 or 8.8% product with an equal amount of water). See Table 1 for examples of products containing triclopyr.

Alternatively, spray or brush the triclopyr solution onto the freshly cut stumps of greenbrier vines for control. There is some soil activity with triclopyr, so do not use products containing triclopyr near desirable landscape plants, and do not allow the triclopyr solution to contact the trunks, stems, or foliage of desirable plants. Several triclopyr products are available for use in established tall fescue lawns to control broadleaf weeds, and these can be used to control greenbrier growing there. Follow label directions for use and safety.

Table 1. Post-emergence Spray Herbicides for Control of Greenbrier.

Pesticides are updated annually. Last updates were done on 8/21 by Joey Williamson.

Originally published 12/17